The time frame here is addressed confidently at around 14,500 years ago
and compares with the other date I have often remarked upon at 12,900 years
ago. They may not be the same events but
it must be said, that unless carbon dating here is successfully cross
correlated with a secure source of chronology, the 12,900 dating is highly
susceptible to underestimation as happened to the first six thousand years of
comparables which needed many centuries of correction. The same could be easily true here.
It also begs one other question.
The Pleistocene Nonconformity itself was a planned event otherwise
extraordinarily improbable. It is
reasonable that it was used to successfully correct a natural crustal shift
that had taken place much earlier and demonstrated the possibilities. I really do not see how it could have been
chanced otherwise.
The other evidence cited here readily conforms to the effects of the
Pleistocene nonconformity until we are able to develop better resolution.
Coral Links Ice Sheet Collapse
to Ancient 'Mega Flood'
ScienceDaily (Apr. 3,
2012) — Coral off Tahiti has linked the collapse of massive ice sheets
14,600 years ago to a dramatic and rapid rise in global sea-levels of around 14
metres.
Previous research could not
accurately date the sea-level rise but now an Aix-Marseille University-led
team, including Oxford University scientists Alex Thomas and Gideon Henderson,
has confirmed that the event occurred 14,650-14,310 years ago at the same time
as a period of rapid climate change known as the Bølling warming.
The finding will help
scientists currently modelling future climate change scenarios to factor in the
dynamic behaviour of major ice sheets.
A report of the research is
published in this week's Nature.
'It is vital that we look into
Earth's geological past to understand rare but high impact events, such as the
collapse of giant ice sheets that occurred 14,600 years ago,' said Dr Alex
Thomas of Oxford University's Department of Earth Sciences, an author of the
paper. 'Our work gives a window onto an extreme event in which deglaciation
coincided with a dramatic and rapid rise in global sea levels -- an ancient
'mega flood'. Sea level rose more than ten times more quickly than it is rising
now! This is an excellent test bed for climate models: if they can reproduce
this extraordinary event, it will improve confidence that they can also predict
future change accurately.'
During the Bølling warming
high latitudes of the Northern hemisphere warmed as much as 15 degrees Celsius
in a few tens of decades. The team has used dating evidence from Tahitian
corals to constrain the sea level rise to within a period of 350 years,
although the actual rise may well have occurred much more quickly and would
have been distributed unevenly around the world's shorelines.
Dr Thomas said: 'The Tahitian
coral is important because samples, thousands of years old, can be dated to
within plus or minus 30 years. Because Tahiti is an ocean island, far away from
major ice sheets, sea-level evidence from its coral reefs gives us close to
the 'magic' average of sea levels across the globe, it is also subsiding into
the ocean at a steady pace that we can easily adjust for.'
The research is part of a
large international consortium, the Integrated Ocean Drilling Program (IODP),
and the coral samples were obtained by drilling down to the sea floor from a
ship positioned off the coast of Tahiti.
What exactly caused the
Bølling warming is a matter of intense debate: a leading theory is that the
ocean's circulation changed so that more heat was transported into Northern
latitudes.
The new sea-level evidence
suggests that a considerable portion of the water causing the sea-level rise at
this time must have come from melting of the ice sheets in Antarctica, which
sent a 'pulse' of freshwater around the globe. However, whether the freshwater
pulse helped to warm the climate or was a result of an already warming world remains
unclear.
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